There exist many assemblies intended for directional coring and drilling but those which are known at the present time require a prior operation of fitting the guidance or sidetracking element, separately from the operation of lowering the core barrel and using the latter. This succession of operations takes a great deal of time which, as is known, is very expensive in this industry because of the particular specialization of the individuals practicing it, the risks which they run, the dedicated equipment used, the technical complexity of the operations which have to be performed, etc. There are also the risks of losing expensive equipment in the ground in each lowering and raising operation and, often because of this, also losing access to the borehole.